That is absolutely true but teachers, now in an appalling position, played a large part in their own downfall.
They allowed pupils to speak back, then they decided that pupils should be listened to all times and that they must jump if a parent complained.
They didn't insist on a parent making a complaint to the school should make an appointment at the teacher's convenience and be given a set time in which to make it; not assume that if a parent made a complaint they should be treated as if they were Moses carrying the Ten Commandments.
It's a long path back but an easy step would be to say parents cannot have easy access. They must have a timed appointment at the teacher's convenience. No easy access. The matter is either important enough for the parent to inconvenience themselves or it is not.
If the parent turns up inappropriately dressed (code for saying, this is how little I think of you) the appointment is cancelled. The appointment is given a certain time, when that's reached, off they go.
If the parent becomes abusive, they are told to leave and take their child with them. if they refuse to do this, the police are called.
It would have the effect of making the school a place where respect is demanded, or at least the appearance of respect and that will do.
They must take off the "Piss on me I'm free label" and put on a "Very Very Expensive label".
Value yourself at nothing and in two minutes everyone will do the same.
Of course, this won't happen and some of those who would object will be teachers themselves! You couldn't make it up!